Experimental and thermodynamic correlation of 4-hydroxycoumarin solubility in aqueous-organic solvent systems (DMSO, ACN, DMF) at eight temperatures

• Equilibrium Solubility of 4-hydroxycoumarin was highest in DMF and lowest in water at all temperatures. • Aqueous–organic solvent mixtures markedly enhanced solubility over pure water. • Experimental solubility data were well correlated using van’t Hoff, Apelblat, and λh models. • Results enable informed solvent selection for efficient extraction and purification of 4-hydroxycoumarin. The solid–liquid equilibrium solubility of 4-hydroxycoumarin (4-HC) was investigated in pure water, pure organic solvents (DMF, ACN, and DMSO), and their aqueous binary mixtures at eight temperatures ranging from 288.15 to 323.15 K under atmospheric pressure. Solubility measurements were performed using a gravimetric method employing a Shimadzu analytical balance, a thermostatic water bath, a shaker, and a vacuum filtration system. The effects of solvent composition and temperature on 4-HC solubility were systematically examined. The results indicate that solubility is strongly influenced by both factors, with significantly enhanced solubility in aqueous–organic mixtures compared to pure water. The van’t Hoff model, the modified Apelblat equation, and the λh model were applied to correlate the experimental data, all showing good agreement with measured values. The resulting insights and model parameters provide useful guidance for optimizing pharmaceutical processes and improving industrial extraction and purification strategies for 4-HC.